In general, digitally controlled current driver circuits that can change output current magnitude by changing digital signals are presented. For example, JP-3868836 B2 shows it. In JP-3868836 B2 discloses circuit topology having a D/A converter and a current amplifier. The D/A converter is constructed by a bipolar transistor or a MOS transistor. The current amplifier amplifies the current from the D/A converter. Current driver circuits are used for circuits for LED driving, organic EL driving or communication.
When a technique in JP-3868836 B2 is applied, area of circuit is increased since the current amplifier is necessary after the output terminal of the D/A converter. Further, if the circuit topology shown in JP-3868836 B2 is applied with the current amplifier provided by the MOS transistor, slew rate of the output current waveform is degraded since the response of the output current changing can not be with the fast input current changing.